Sign up to receive free email alerts when patent applications with chosen keywords are publishedSIGN UP

Abstract:

An electronic sphygmomanometer has a causing unit that causes a constant
volume change in a cuff and a causing processing unit for controlling a
drive of the causing unit for a period for which a first pressure control
(for example, depressurization control) is made so as to execute a
process for giving a constant volume change to the cuff. Further, the
electronic sphygmomanometer includes a measurement control unit that
controls based on a cuff pressure signal measurement of a pulse wave
amplitude and a pressure change property with respect to the volume
change. The electronic sphygmomanometer includes a correction processing
unit that corrects the measured pulse wave amplitude based on the
measured pressure change property and a blood pressure calculating unit
that calculates a blood pressure value based on the corrected pulse wave
amplitude.

Claims:

1. An electronic sphygmomanometer, comprising: a cuff capable of being
wrapped around a measurement site; a pressure adjustment unit that
adjusts a pressure in the cuff; a pressure sensor that detects a cuff
pressure signal representing the pressure in the cuff; a causing unit
that causes a constant volume change in the cuff; a first pressure
control unit that controls drive of the pressure adjustment unit so as to
make a first pressure control for changing the pressure in the cuff to a
specified direction; a causing processing unit that controls drive of the
causing unit for a period for which the first pressure control is made
and executes a process for causing the constant volume change in the
cuff; a measurement control unit that controls measurement of a pressure
change property with respect to the volume change based on the cuff
pressure signal acquired at the time of executing a process of the
causing processing unit and measurement of the pulse wave amplitude based
on the cuff pressure signal; a correction processing unit that corrects
the pulse wave amplitude based on the measured pressure change property;
and a blood pressure calculating unit that calculates a blood pressure
value based on the corrected pulse wave amplitude.

2. The electronic sphygmomanometer according to claim 1, wherein the
causing processing unit causes the volume change successively at a cycle
different from that of a heart rate of a person to be measured during a
period of the first pressure control, and wherein the measurement control
unit comprises: an acquiring unit that acquires the cuff pressure signal
in chronological order during the period of the first pressure control,
and a separation unit that executes a filter process on the acquired cuff
pressure signal so as to separate the acquired cuff pressure signal into
the pulse wave amplitude and the pressure change property.

3. The electronic sphygmomanometer according to claim 2, wherein the
first pressure control is a depressurization control, and wherein the
heart rate is calculated based on the cuff pressure signal during
pressurization control before transition to the depressurization control.

4. The electronic sphygmomanometer according to claim 1, wherein the
causing processing unit causes the volume change at a constant interval
during the period of the first pressure control, and wherein the
measurement control unit comprises: a first measurement processing unit
that measures the pressure change property based on the cuff pressure
signal output at a specified segment where the volume change is given to
the cuff, and a second measurement processing unit that measures the
pulse wave amplitude based on the cuff pressure signal output during the
period of the first pressure control and at a segment other than the
specified segment.

5. The electronic sphygmomanometer according to claim 4, wherein when the
pressure in cuff has the same pressure value, the first pressure control
unit makes the first pressure control in stages in order to measure an
amplitude value of the cuff pressure signal at times when the volume
change is caused and is not caused.

6. The electronic sphygmomanometer according to claim 4, wherein the
causing processing unit causes the volume change at a segment from a
maximum point of the cuff pressure signal to next rising point.

7. The electronic sphygmomanometer according to claim 1, wherein the cuff
includes a fluid bladder for blood pressure measurement, and a blood flow
blocking unit arranged on an upper-stream side with respect to the fluid
bladder, the electronic sphygmomanometer further comprising: a second
pressure control unit that makes a second pressure control in order to
change the pressure in the cuff to a direction opposite to the specified
direction; and a blood flow blocking unit that blocks a blood flow of the
measurement site using the blood flow blocking unit only for the period
of the first pressure control, wherein the causing processing unit causes
the volume change sequentially during the period of the first pressure
control, and wherein the measurement control unit comprises: a first
measurement processing unit that measures the pressure change property
based on the cuff pressure signal output during the period of the first
pressure control, and a second measurement processing unit that measures
the pulse wave amplitude based on the cuff pressure signal output during
the period of the second pressure control.

8. The electronic sphygmomanometer according to claim 1, wherein the
causing unit includes a cylinder and a drive unit for driving the
cylinder.

Description:

BACKGROUND OF THE INVENTION

[0001] 1. Technical Field

[0002] The present invention relates to an electronic sphygmomanometer,
and particularly relates to the electronic sphygmomanometer that detects
a volume change of a blood vessel as a pressure change of a cuff, namely,
an amplitude of a pressure pulse wave, and calculates a blood pressure
value using the detected amplitude of the pressure pulse wave.

[0003] 2. Background Art

[0004] Electronic sphygmomanometers for measuring a blood pressure using
an amplitude of a pressure pulse wave (hereinafter, "a pulse wave
amplitude") like in an oscillometric method have been conventionally
present. The oscillometric method is a method for pressurizing or
depressurizing a cuff wrapped around a part of an organism to acquire a
volume change of the cuff obtained from a volume change of a pressurized
blood vessel as a pressure change of the cuff, namely, the pulse wave
amplitude and calculating a blood pressure.

[0005] In such electronic sphygmomanometers, it is found that because a
pressure and a volume of a cuff are not in proportional to each other due
to a cuff property, detection accuracy of a volume change in a blood
vessel varies according to an arm circumference and pressures of a cuff.
That is to say, even if the same blood pressure values are obtained, an
error is caused in a level of the pulse wave amplitude due to factors
such as differences in the cuff pressure and the arm circumference. For
this reason, such factors are error factors of the blood pressure value.

[0006] The following method has been conventionally proposed for preparing
a volume change property.

[0007] For example, Japanese Unexamined Patent Publication No. 5-329113
(Patent Document 1) describes a method for preparing a volume change
property of a cuff with respect to a cuff pressure in advance and
converting a signal of the pressure change of the cuff into a volume
change so as to measure a blood pressure value using the volume change.

[0009] In the above method, a pressure of a cuff and a volume change
property need to be acquired in advance. However, the volume change
property changes infinitely according to a wrapping state of the cuff, an
arm circumference and body flexibility. Further, volume change properties
of a pump, a valve and a cuff vary also according to temperature,
humidity or a secular change. For this reason, in the method where the
volume change property is acquired in advance, it is difficult to
properly convert a signal of a cuff pressure change into a volume change.

[0010] Embodiments of the present invention provide an electronic
sphygmomanometer that can accurately calculate a blood pressure value
even if a wrapping state of a cuff and an arm circumference vary.

[0011] An electronic sphygmomanometer according to one or more embodiments
of the present invention includes: a cuff to be wrapped around a
measurement site; a pressure adjustment unit for adjusting a pressure in
the cuff; a pressure sensor for detecting a cuff pressure signal
representing the pressure in the cuff; a causing unit for causing a
constant volume change in the cuff; a first pressure control unit for
controlling drive of the pressure adjustment unit so as to make a first
pressure control for changing the pressure in the cuff to a specified
direction; a causing processing unit for controlling drive of the causing
unit for a period for which the first pressure control is made and
executing a process for causing the constant volume change in the cuff; a
measurement control unit for making controls so as to measure a pressure
change property with respect to the volume change based on the cuff
pressure signal acquired at the time of executing a process of the
causing processing unit and measure the pulse wave amplitude based on the
cuff pressure signal; a correction processing unit for correcting the
measured pulse wave amplitude based on the measured pressure change
property; and a blood pressure calculating unit for calculating a blood
pressure value based on the corrected pulse wave amplitude.

[0012] According to one or more embodiments of the present invention, the
causing processing unit causes the volume change successively at a cycle
different from that of a heart rate of a person to be measured during a
period of the first pressure control, and the measurement control unit
includes an acquiring unit for acquiring the cuff pressure signal in
chronological order during the period of the first pressure control, and
a separation unit for executing a filter process on the acquired cuff
pressure signal so as to separate the acquired cuff pressure signal into
the pulse wave amplitude and the pressure change property.

[0013] According to one or more embodiments of the present invention, the
first pressure control is a depressurization control, and the heart rate
is calculated based on the cuff pressure signal during pressurization
control before transition to the depressurization control.

[0014] According to one or more embodiments of the present invention, the
causing processing unit causes the volume change at a constant interval
during the period of the first pressure control, and the measurement
control unit includes a first measurement processing unit for measuring
the pressure change property based on the cuff pressure signal output at
a specified segment where the volume change is given to the cuff, and a
second measurement processing unit for measuring the pulse wave amplitude
based on the cuff pressure signal output during the period of the first
pressure control and at a segment other than the specified segment.

[0015] According to one or more embodiments of the present invention, when
the pressure in a cuff has the same pressure value, the first pressure
control unit makes the first pressure control in stages in order to
measure an amplitude value of the cuff pressure signal at times when the
volume change is caused and is not caused.

[0016] According to one or more embodiments of the present invention, the
causing processing unit causes the volume change at a segment from a
maximum point of the cuff pressure signal to a next rising point.

[0017] According to one or more embodiments of the present disclosure, the
cuff includes a fluid bladder for blood pressure measurement, and a blood
flow blocking unit arranged on an upper-stream side with respect to the
fluid bladder. A second pressure control unit for making a second
pressure control in order to change the pressure in the cuff to a
direction opposite to the specified direction, and a blood flow block
processing unit for blocking a blood flow of the measurement site using
the blood flow blocking unit only for the period of the first pressure
control are further provided. The causing processing unit causes the
volume change sequentially during the period of the first pressure
control. The measurement control unit includes a first measurement
processing unit for measuring the pressure change property based on the
cuff pressure signal output during the period of the first pressure
control, and a second measurement processing unit for measuring the pulse
wave amplitude based on the cuff pressure signal output during the period
of the second pressure control.

[0018] According to one or more embodiments of the present invention, the
blood flow blocking unit is a fluid bladder for blocking the blood flow.

[0019] According to one or more embodiments of the present invention, the
causing unit includes a cylinder and a drive unit for driving the
cylinder.

[0020] Accordingly to one or more embodiments of the present invention,
the drive unit includes a stepping motor.

[0021] According to the present invention, a pressure change property is
measured, and the pulse wave amplitude is corrected based on the measured
pressure change property. Therefore, a blood pressure value can be
accurately calculated regardless of a wrapping state of the cuff and an
arm circumference.

BRIEF DESCRIPTION OF THE DRAWINGS

[0022] FIG. 1 is an external perspective view illustrating an electronic
sphygmomanometer according to one or more embodiments of the present
invention.

[0023] FIGS. 2(A) and 2(B) are diagrams illustrating typical examples of a
pressure change with respect to a constant volume change caused by a
difference in a circumference of a measurement site.

[0024] FIGS. 3(A) and 3(B) are diagrams illustrating typical examples of
the pressure change with respect to the constant volume change caused by
a difference in a wrapping state of a cuff.

[0025]FIG. 4 is a block diagram illustrating a hardware configuration of
the electronic sphygmomanometer according to one or more embodiments of
the present invention.

[0026] FIG. 5 is a functional block diagram illustrating a functional
constitution of the electronic sphygmomanometer according to one or more
embodiments of the present invention.

[0027] FIGS. 6(A) to 6(F) are diagrams illustrating a concept of a blood
pressure measuring method according to the one or more embodiments of the
present invention.

[0028] FIG. 7 is a flowchart illustrating a blood pressure measuring
process according to one or more embodiments of the present invention.

[0029] FIGS. 8(A) to 8(D) are diagrams for describing a process for
correcting a pulse wave amplitude according to one or more embodiments of
the present invention.

[0030] FIGS. 9(A) and 9(B) are diagrams illustrating detection timings of
a pulse wave amplitude and a pressure change property according to one or
more embodiments of the present invention.

[0031] FIGS. 10(A) and 10(B) are diagrams illustrating another examples of
the detection timings of the pulse wave amplitude and the pressure change
property according to one or more embodiments of the present invention.

[0032] FIG. 11 is a functional block diagram illustrating a functional
constitution of the electronic sphygmomanometer according to one or more
embodiments of the present invention.

[0033] FIG. 12 is a flowchart illustrating the blood pressure measuring
process according to one or more embodiments of the present invention.

[0034]FIG. 13 is a diagram illustrating the detection timings of the
pulse wave amplitude and the pressure change property according to one or
more embodiments of the present invention.

[0035]FIG. 14 is a block diagram illustrating a hardware configuration of
the electronic sphygmomanometer according to one or more embodiments of
the present invention.

[0036] FIG. 15 is a functional block diagram illustrating a functional
constitution of the electronic sphygmomanometer according to one or more
embodiments of the present invention.

[0037] FIG. 16 is a flowchart illustrating the blood pressure measuring
process according to one or more embodiments of the present invention.

DETAILED DESCRIPTION

[0038] One or more embodiments of the present invention will be described
in detail with reference to the drawings. The same reference numerals are
denoted to the same or corresponding portions in the figures, and the
description thereof will not be repeated. Further, in embodiments of the
invention, numerous specific details are set forth in order to provide a
more thorough understanding of the invention. However, it will be
apparent to one of ordinary skill in the art that the invention may be
practiced without these specific details. In other instances, well-known
features have not been described in detail to avoid obscuring the
invention.

First Example

With Regard to Appearance

[0039] At first, an appearance of an electronic sphygmomanometer
(hereinafter, "a sphygmomanometer") according to one or more embodiments
of the present invention will be described below.

[0040] FIG. 1 is an external perspective view illustrating a
sphygmomanometer 1 according to one or more embodiments of the present
invention. The sphygmomanometer 1 calculates a blood pressure value in a
manner that a predetermined algorithm is applied to a pulse wave
amplitude (an amplitude of a pressure pulse wave) similarly to the
oscillometric method.

[0041] With reference to FIG. 1, the sphygmomanometer 1 has a main body
portion 10, a cuff 20 that can be wrapped around a predetermined
measurement site of a person to be measured (for example, an upper arm),
and an air tube 31 for connecting the main body portion 10 and cuff 20. A
display unit 40 formed by liquid crystal, for example, and an operation
unit 41 for accepting instructions from a user (typically the person to
be measured) are arranged on a surface of the main body portion 10.

[0042] The operation unit 41 has, for example, a power switch 41A for
accepting inputs of instructions for powering ON/OFF, a measurement
switch 41B for accepting an instruction for starting a measurement, a
setting switch 41C for accepting instructions relating to various setting
processes, and a memory switch 41D for accepting instructions for reading
and displaying past stored values. The operation unit 41 may further has
an ID switch (not shown) that is operated in order to input ID
(identification) information for identifying a person to be measured.

[0043] A summary of one or more embodiments of the present invention will
be described herein.

[0044] When a blood pressure is measured based on a pulse wave amplitude
like the oscillometric method, it is necessary to eliminate error factors
caused by not only differences in the cuff pressure but also differences
in a wrapping state of the cuff (tight/loose), an arm circumference, and
body flexibility in order to accurately calculate a blood pressure value.

[0045] Therefore, in accordance with one or more embodiments of the
present invention, a constant volume change is caused at every time of
measurement (during pressurization or depressurization), the pulse wave
amplitude due to a change in an internal pressure of a blood vessel and a
property of a pressure change with respect to the constant volume change
(hereinafter, "a pressure change property") are measured. As a result,
the pressure change property can be acquired according to various
measurement conditions (for example, an arm circumference and the
wrapping state of the cuff) to be the error factors at every measurement.
This will be described concretely with reference to FIG. 2 and FIG. 3.

[0046] FIGS. 2(A) and 2(B) are diagrams illustrating typical examples of
the pressure change property with respect to the constant volume change
caused by a difference in a circumference of the measurement site. As
shown in FIG. 2(A), the constant volume change is given to the cuff
during pressurization or depressurization. FIG. 2(B) illustrates a
difference in the pressure change property due to the difference in the
circumference of the measurement site when the constant volume change is
given to the cuff. The pressure change amplitude in a pressure change
property 501 at the time when the measurement site is thinner than a
standard size is comparatively larger than that of a pressure change
property 502 at the time when the measurement site is thicker than the
standard size. Both of them have different change rates.

[0047] FIGS. 3(A) and 3(B) are diagrams illustrating typical examples of
the pressure change property with respect to the constant volume change
due to the difference in the wrapping state of the cuff. As shown in FIG.
3(A), the constant volume change is given to the cuff during
pressurization or depressurization. FIG. 3(B) illustrates the difference
in the pressure change property due to the difference in the wrapping
state of the cuff when the constant volume change is given to the cuff.
The pressure change amplitude in a pressure change property 511 at the
time when the cuff is wrapped tightly around the measurement site is
comparatively larger than that in a pressure change property 512 at the
time when the cuff is wrapped loosely around the measurement site.

[0048] In accordance with one or more embodiments of the present
invention, the constant volume change is caused in the cuff at every time
of measurement (during pressurization or depressurization), and the pulse
wave amplitude caused by the volume change in a blood vessel and the
pressure change property with respect to the constant volume change are
measured. The pulse wave amplitude is corrected by using the measured
pressure change property, and a predetermined algorithm is applied to the
corrected value of the pulse wave amplitude so that a blood pressure
value is calculated.

[0049] A constitution and an operation of the sphygmomanometer 1 according
to one or more embodiments of the present invention will be described
concretely below.

(With Regard to Hardware Configuration)

[0050]FIG. 4 is a block diagram illustrating the hardware configuration
of the sphygmomanometer 1 according to one or more embodiments of the
present invention.

[0051] With reference to FIG. 4, the cuff 20 of the sphygmomanometer 1
includes an air bladder 21. The air bladder 21 is connected to an air
system 30 via the air tube 31.

[0052] The main body portion 10 includes the display unit 40, the
operation unit 41, the air system 30, a CPU (Central Processing Unit) 100
for intensively controlling respective sections and executing various
arithmetic processes, a memory unit 42 for storing programs for allowing
the CPU 100 to perform predetermined operations and various data, a
nonvolatile memory (for example, a flash memory) 43 for storing the
measured blood pressure, a power supply 44 for supplying a power to the
CPU 100, a timing unit 45 for performing a timing operation, and a data
input/output unit 46 for accepting data input from an outside.

[0053] The air system 30 includes a pressure sensor 32 for detecting a
pressure (cuff pressure) in the air bladder 21, a pump 51 for supplying
air to the air bladder 21 in order to heighten the cuff pressure, and a
valve 52 that is opened and closed in order to exhaust or seal the air
out from or into the air bladder 21.

[0054] The main body portion 10 further includes an oscillation circuit
33, a pump drive circuit 53, and a valve drive circuit 54 with relation
to the air system 30.

[0055] The pressure sensor 32 is, for example, an electrostatic capacity
type pressure sensor, and its capacity value changes with the cuff
pressure. The oscillation circuit 33 outputs a signal of an oscillation
frequency according to the capacity value of the pressure sensor 32 to
the CPU 100. The CPU 100 converts a signal acquired from the oscillation
circuit 33 into a pressure and detects the pressure. The pump drive
circuit 53 controls drive of the pump 51 based on a control signal given
from the CPU 100. The valve drive circuit 54 controls opening/closing of
the valve 52 based on a control signal given from the CPU 100.

[0056] The pump 51, the valve 52, the pump drive circuit 53 and the valve
drive circuit 54 constitute an adjustment unit 50 for adjusting the cuff
pressure. The devices for adjusting the cuff pressure are not limited to
these.

[0057] The data input/output unit 46 reads and writes programs and data
from and into a detachable recording medium 132, for example. Further/or
the data input/output unit 46 may transmit/receive the programs and data
from an external computer, not shown, via a communication line.

[0058] The above constitution is similar to that of a conventional and
general electronic sphygmomanometer. In accordance with one or more
embodiments of the present invention, the main body portion 10 further
includes a causing unit 60 for causing the constant volume change in the
cuff 20. The causing unit 60 has a cylinder 61 for adjusting the volume
in the cuff 20 at high speed, a motor (for example, a stepping motor) 62
for driving the cylinder 61, and a motor drive circuit 63 for driving the
motor 62.

[0059] The cylinder 61 is connected to the air bladder 21 via the air tube
31. The motor 62 operates a piston (not shown) in the cylinder 61 to an
axial direction of the cylinder 61. As a result, the volume in the
cylinder 61 changes. Accordingly, the volume in the air bladder 21
changes.

[0060] The devices constituting the causing unit 60 are not limited to
these devices as long as the constant volume change can be caused.

[0061] The cuff 20 includes the air bladder 21, but a fluid supplied to
the cuff 20 is not limited to air, and thus may be a liquid or gel.
Instead of the fluid, uniform fine particles such as microbeads may be
used.

[0062] (With Regard to Functional Constitution)

[0063] FIG. 5 is a functional block diagram illustrating a functional
constitution of the sphygmomanometer 1 according to one or more
embodiments of the present invention. FIG. 5 illustrates the functional
constitution of a depressurization measurement method, namely, a method
for calculating a blood pressure value based on a cuff pressure signal
acquired at the time of depressurization.

[0064] With reference to FIG. 5, the CPU 100 includes, as its functions, a
pressurization control unit 102, a depressurization control unit 104, a
causing processing unit 106, a measurement control unit 108, a correction
processing unit 114, a blood pressure calculating unit 116, and an output
processing unit 118. FIG. 5 illustrates only peripheral hardware that
directly transmits/receives signals to/from the respective units of the
CPU 100 in order to simplify the description.

[0065] The pressurization control unit 102 controls the pressurization of
the cuff 20. Concretely, a control signal is transmitted to the pump
drive circuit 53, so that the pump 51 is driven and air is sent to the
air bladder 21.

[0066] The depressurization control unit 104 controls depressurization of
the cuff 20 at, for example, a predetermined speed. Concretely, a control
signal is transmitted to the valve drive circuit 54, so that the valve 52
is driven and air fed to the air bladder 21 is sealed and exhausted.

[0067] In accordance with one or more embodiments of the present
invention, the depressurization control means control that changes the
pressure in the cuff 20 to a specified direction (namely, a falling
direction), and the pressurization control means control that changes the
pressure in the cuff 20 to a direction opposite to the specified
direction (namely, a rising direction).

[0068] The causing processing unit 106 controls the drive of the causing
unit 60 (the motor drive circuit 63) for a period of the depressurization
control so that a process for causing the constant volume change in the
cuff 20 (the air bladder 21) is executed. In accordance with one or more
embodiments of the invention, the volume change is caused successively
during the depressurization control at a cycle different from a cycle of
a heart rate of the person to be measured. The heart rate of the person
to be measured may be calculated by a publicly-known method, for example,
at the time of the pressurization control, or a past (for example,
previous) measured result may be used. In another manner, a numerical
value that is not present as the cycle of the heart rate may be preset as
the cycle different from the cycle of the heart rate of an examinee.

[0069] The measurement control unit 108 makes control based on the cuff
pressure signal (detected by the pressure sensor 32) acquired from the
oscillation circuit 33 so that the pulse wave amplitude and the pressure
change property with respect to the constant volume change are measured.
In accordance with one or more embodiments of the invention, the
measurement control unit 108 includes a signal acquiring unit 110 and a
separation processing unit 112.

[0070] The signal acquiring unit 110 acquires the cuff pressure signals in
chronological order for the period of the depressurization control.
During this period, because the constant volume change is caused in the
air bladder 21, the cuff pressure signals acquired for the period of the
depressurization control are signals obtained by synthesizing the pulse
wave amplitude with the pressure change amplitude with respect to the
constant volume change. That is to say, not only a change in an internal
pressure of a blood vessel but also the pressure change with respect to
the constant volume change are overlapped on the cuff pressure signal
detected by the pressure sensor 32.

[0071] The separation processing unit 112 executes a filter process on the
cuff pressure signal acquired by the signal acquiring unit 110 so as to
separate the cuff pressure signal into the pulse wave amplitude and the
pressure change property.

[0072] The correction processing unit 114 corrects the pulse wave
amplitude measured based on the measured pressure change property. The
blood pressure calculating unit 116 calculates a blood pressure value,
such as, a highest blood pressure and a lowest blood pressure based on
the corrected pulse wave amplitude. The output processing unit 118
executes a process for outputting the blood pressure value. For example,
the blood pressure value is displayed on the display unit 40, and the
blood pressure value is stored in the flash memory 43.

[0073] The operations of the above-described functional blocks may be
realized by executing software stored in the memory unit 42, or at least
one of the functional blocks may be realized by hardware.

[0074] Concept of a blood pressure measuring method according to one or
more embodiments of the invention will be described with reference to
FIGS. 6(A) to 6(F). FIGS. 6(A) to 6(F) are diagrams illustrating the
concept of the blood pressure measuring method according to one or more
embodiments of the present invention.

[0075] FIG. 6(A) illustrates a change in an intra-arterial pressure along
a temporal axis. FIG. 6(B) illustrates a volume change along the same
temporal axis as that in FIG. 6(A). In accordance with one or more
embodiments of the present invention, the constant volume change shown in
FIG. 6(B) is given to the cuff 20 during the depressurizing of the cuff
20. In this case, the cuff pressure signal acquired via the oscillation
circuit 33 has a waveform as shown in FIGS. 6(C) and 6(D). FIG. 6(D)
illustrates a partially enlarged diagram of a part 401 of the cuff
pressure signal in FIG. 6(C). As shown in FIG. 6(D), the pressure change
with respect to the constant volume change is overlapped with the cuff
pressure signal.

[0076] In accordance with one or more embodiments of the present
invention, the cuff pressure signal including the pressure change with
respect to the constant volume change is subject to, for example, the
filter process so as to be separated into the pulse wave amplitude (FIG.
6(E)) caused by the change in the internal pressure in the blood vessel
and the pressure change amplitude caused by the constant volume change,
namely, the pressure change property (FIG. 6(F)).

[0077] The concrete correcting method in the correction processing unit
114 will be described later.

(With Regard to Operation)

[0078] FIG. 7 is a flowchart illustrating a blood pressure measuring
process according to one or more embodiments of the present invention.
The process shown in the flowchart in FIG. 7 is stored as a program in
the memory unit 42 in advance. The CPU 100 reads and executes this
program so that the function of the blood pressure measuring process is
realized.

[0079] With reference to FIG. 7, the pressurization control unit 102
pressurizes the cuff 20 (step S2). During the pressurization, the
pressurization control unit 102 calculates a heart rate based on an
output from the oscillation circuit 33 by a publicly-known method (step
S4).

[0080] The pressurization control unit 102 determines whether the pressure
in the cuff 20 (the cuff pressure) is a predetermined value (for example,
200 mmHg) (step S6). When the determination is made that the cuff
pressure does not reach the predetermined value (NO in step S6), the
sequence returns to step S2, and the above process is repeated. When the
determination is made that the cuff pressure reaches the predetermined
value (YES in step S6), the pressurization is stopped (step S8). In
accordance with one or more embodiments of the present invention, the
pressurization is stopped when the cuff pressure reaches the
predetermined value, but at the time when the highest blood pressure is
estimated during the pressurization, the pressurization may be stopped
like a conventional method.

[0081] The depressurization control unit 104 then starts to depressurize
the cuff 20 (step S10). At the same time, the causing processing unit 106
causes the constant volume change in the cuff 20 (step S12). Concretely,
a control signal is transmitted to the motor drive circuit 63, so that
the cylinder 61 is driven at a high speed, and the constant volume change
is given to the air bladder 21. A cycle different from that of the heart
rate of the person to be measured calculated in step S4 is selected as
the cycle of the volume change.

[0082] The signal acquiring unit 110 of the measurement control unit 108
acquires cuff pressure data (the cuff pressure signal) detected by the
pressure sensor 32 during the depressurization (step S14). The acquired
cuff pressure data is stored in the memory unit 42 in chronological
order.

[0083] The depressurization control unit 104 then determines whether the
cuff pressure reaches a predetermined value (for example, 40 mmHg) (step
S15). When the determination is made that the cuff pressure does not
reach the predetermined value (NO in step S15), the sequence returns to
step S12, and the above process is repeated. When the determination is
made that the cuff pressure reaches the predetermined value (YES in step
S15), the depressurization control is ended and the sequence goes to step
S16. In accordance with one or more embodiments of the present invention,
when the cuff pressure reaches the predetermined value, the
depressurization control is ended, but at the time when the blood
pressure can be calculated (for example, at the time of the lowest blood
pressure value estimated during the pressurization or less, at the time
when the amplitude is smaller than a predetermined value or the like),
the depressurization control may be ended.

[0084] In step S16, the separation processing unit 112 of the measurement
control unit 108 filtrates the cuff pressure data acquired in
chronological order in step S14 to separate the data into the pulse wave
amplitude and the pressure change property. Concretely, for example, a
filter process for eliminating a high-frequency component from the cuff
pressure data and a filter process for extracting the high-frequency
component are executed in parallel. As a result, the pulse wave amplitude
and the pressure change property can be extracted.

[0085] Thereafter, the correction processing unit 114 corrects the pulse
wave amplitude acquired in step S16. Concretely, an envelope curve of a
value string of the pulse wave amplitude is formed (step S18), and the
formed envelope curve is corrected by using the pressure change property
obtained in step S16 (step S20). Such a process for correcting the pulse
wave amplitude will be described in detail with reference to FIG. 8.

[0086] FIGS. 8(A) to 8(D) are diagrams for describing the process for
correcting the pulse wave amplitude according to one or more embodiments
of the present invention.

[0087] FIG. 8(A) illustrates an example of the envelope curve 401 formed
in step S18. FIG. 8(B) illustrates an example of a line representing the
pressure change property acquired in step S16 (hereinafter,
"characteristic line") 402.

[0088] The correction processing unit 114 detects the cuff pressure PCm
corresponding to a maximum point 4011 of the envelope curve 401. The cuff
pressure PCm corresponds to an average blood pressure (MAP). The
correction processing unit 114 uses a point 4021 corresponding to the
cuff pressure PCm on the characteristic line 402 as a standard, and
corrects the envelope curve 401 so that characteristic line 402 has a
constant amplitude. That is to say, the envelope curve 401 is corrected
so that the characteristic line 402 becomes a straight line 4022 passing
through the point 4021. FIG. 8(C) illustrates a corrected envelope curve
403. In the corrected envelope curve 403, a side lower than the cuff
pressure PCm is revised upward, and a side lower than the cuff pressure
PCm is revised downward.

[0089] With reference to FIG. 7 and FIG. 8(D), the blood pressure
calculating unit 116 calculates a highest blood pressure (SYS) and a
lowest blood pressure (DIA) (step S22) based on the corrected envelope
curve 403. Concretely, the calculation is carried out in the following
manner. That is to say, a value obtained by multiplying the maximum point
4011 of the envelope curve 403 by a predetermined constant (for example,
0.5) is determined as a threshold TH1, and a value obtained by
multiplying the maximum point 4011 by a predetermined constant (for
example, 0.7) is determined as the threshold TH2. The cuff pressure that
is higher than the average blood pressure (MAP) and corresponds to a
point at which the corrected envelope curve 403 and the threshold TH1
intersect is determined as the highest blood pressure (SYS). The cuff
pressure that is lower than the average blood pressure (MAP) and
corresponds to a point at which the corrected envelope curve 403 and the
threshold TH2 intersect is determined as the lowest blood pressure (DIA).

[0090] The blood pressure calculating unit 116 may calculate a heart rate
based on the pulse wave amplitude acquired by the separating process
according to a publicly-known method.

[0091] Finally, air is exhausted from the air bladder 21 (step S24), and
the output processing unit 118 displays and records measured results (the
highest blood pressure, the lowest blood pressure and the heart rate)
(step S26). The flash memory 43 stores measurement data in which, for
example, the measured values (the highest blood pressure, the lowest
blood pressure, and the heart rate) are related to measurement time and
dates in a record format.

[0092] The blood pressure measuring process according to one or more
embodiments of the present invention is ended with the above-described
manner. The exhausting process (step S24) may be executed in parallel
with the process in steps S16 to S22.

[0093] As described above, according to one or more embodiments of the
present invention, the pressure change property is extracted at every
measurement. For this reason, influences of the wrapping state of the
cuff 20 and secular changes in the pump 51, the valve 52 and the cuff 20
are securely reflected on the pressure change property. In accordance
with one or more embodiments of the present invention, the pulse wave
amplitude caused by the change in the internal pressure in the blood
vessel is corrected based on such a pressure change property, and the
blood pressure value is calculated. Therefore, the blood pressure value
can be accurately measured regardless of the wrapping state of the cuff
20 and the secular changes in the pump 51, the valve 52 and the cuff 20.

[0094] In accordance with one or more embodiments, the envelope curve is
formed based on the waveform (the pulse wave amplitude) from which the
influence of the pressure change with respect to the constant volume
change is eliminated by filtration, but may be formed based on the
amplitude of the cuff pressure signal before filtration.

[0095] Embodiments described above with respect to the first example
describe a depressurization measuring method as the example, but one or
more embodiments of the present invention can be applied also to the
pressurization measuring method. In this case, the constant volume change
is caused during a period of the pressurization control, and the cuff
pressure signal may be acquired during the period of the pressurization
control.

Second Example

[0096] One or more embodiments of a second example of the present
invention will be described below.

[0097] As described above, in accordance with one or more embodiments of
the present invention the constant volume change is caused at a cycle
different from that of a heart rate of a person to be measured during the
period of the pressure control (the depressurization control) for which
the pulse wave amplitude is measured. The cuff pressure data, in which
the pressure change is overlapped with the constant volume change, is
subject to the filter process, so that the pressure change property is
extracted.

[0098] However, in accordance with one or more embodiments of the present
invention, the constant volume change is caused at a constant interval
(successively) during the period of the pressure control for which the
pulse wave amplitude is measured. Amplitude values of the cuff pressure
signal are measured when the volume change is caused and is not caused,
so that the pressure change property is measured without the filter
process.

[0099] In accordance with one or more embodiments of the present
invention, the stepwise pressure control (so-called step
depressurization) is made so that the cuff pressure signals at the times
when the constant volume is caused and is not caused are measured when
the pressure values in the cuff are equal. The pulse wave amplitude and
the pressure change property are calculated based on the two kinds of
measured cuff pressure signals.

[0100] FIGS. 9(A) and 9(B) are diagrams illustrating detection timings of
the pulse wave amplitude and the pressure change property according to
one or more embodiments of the present invention. FIG. 9(A) illustrates
the cuff pressure as the control value along a temporal axis. FIG. 9(B)
illustrates the cuff pressure signal (mainly, a pulse wave) along the
same temporal axis as that of FIG. 9(A). In FIG. 9(B), a segment TA is a
period for which the pulse wave is detected. That is to say, the segment
TA represents a detection period of the cuff pressure signal to be used
for calculation of the pulse wave amplitude. A segment TB is a period for
which the constant volume change is caused. Therefore, the segment TB
represents the detection period of the cuff pressure signal to be used
for the calculation of the pressure change property.

[0101] In accordance with one or more embodiments of the present
invention, the segment TA is a segment from start to end of one beat of a
pulse wave (a rising point of the pulse wave to a rising point of next
pulse wave), and the segment TB is a partial segment of next pulse wave
in the segment TA.

[0102] In such a manner, the constant volume change is caused on the same
position at every time in the same cycle as that of the heart rate of the
person to be measured, so that the pressure change property (the line
representing this) can be obtained.

[0103] The segment TA may include at least the rising point of one beat of
a pulse wave or the rising point of next pulse wave, and a maximum point
of the pulse wave therebetween. The segment TB may be a segment that does
not include the rising point of one beat of a pulse wave, the rising
point of next pulse wave and the maximum point of the pulse wave
therebetween. Therefore, when the segment TA includes the rising point of
one beat of a pulse wave through the rising point of next pulse wave as
shown in FIG. 9(B), the segment TB may be included in the segment TA.
That is to say, in accordance with one or more embodiments of the present
invention, the pulse wave amplitude and the pressure change property are
measured in series but may be measured in parallel.

[0104] The period represented by the segment TB is the time shorter than
the cycle of the heart rate and may be predetermined, or determined at
every measurement.

[0105] As shown in FIG. 9(A), the pressure in the cuff is maintained until
the pulse wave amplitude and the pressure change property are measured
(more specifically, the cuff pressure data that can be used for the
calculation of the pulse wave amplitude and the pressure change property
is collected). When the pulse wave amplitude and the pressure change
property are measured, the depressurization to a predetermined pressure
is carried out. As a result, the pulse wave amplitude and the pressure
change property can be acquired for the depressurization period without
filtrating the cuff pressure signal.

[0106] In order to acquire the pulse wave amplitude and the pressure
change property, it is not necessary to carry out such step
depressurization. As shown in FIGS. 10(A) and 10(B), both of them may be
detected at every pulse at a predetermined speed during the
depressurization. FIG. 10(A) illustrates the cuff pressure as the control
value along a temporal axis. FIG. 10(B) illustrates the cuff pressure
signal (mainly, the pulse wave) along the same temporal axis as that in
FIG. 10(A). As shown in FIG. 10(B), a segment from the rising point of
one beat of a pulse wave to the maximum point may be represented by a
segment TA# (a period for detecting the pulse wave), and at least a
partial segment from the maximum point of the pulse wave to the rising
point of next pulse wave may be represented by a segment TB# (a period
for causing the constant volume change).

[0107] The constitution and the basic operation of the sphygmomanometer in
accordance with embodiments of the second example are similar to the
embodiments in the first example. Therefore, the description uses
reference symbols used with respect to the first example is given.

[0108] Only portions different from the first example will be described
below.

[0109] (With Regard to Functional Constitution)

[0110] FIG. 11 is a functional block diagram illustrating a functional
constitution of the sphygmomanometer 1 according to one or more
embodiments of the present invention. FIG. 11 also illustrates a
functional constitution of the depressurizing measuring method.
Functional blocks that execute the similar processes to those in the
functional blocks shown in FIG. 5 are denoted by the same reference
symbols. Therefore, the description thereof will not be repeated.

[0111] With reference to FIG. 11, in accordance with one or more
embodiments of the second example, the CPU 100 includes a
depressurization control unit 104A, a causing processing unit 106A and a
measurement control unit 108A instead of the depressurization control
unit 104, the causing processing unit 106 and the measurement control
unit 108 as previously described.

[0112] The depressurization control unit 104A makes the stepwise
depressurization control, namely, the step depressurization. The causing
processing unit 106A causes the constant volume change at a constant
interval during the period of the depressurization control. In accordance
with one or more embodiments of the present invention, start timing at
which the constant volume change is caused is preferably the same cycle
as that of the heart rate of the person to be measured.

[0113] The measurement control unit 108A includes a first measurement unit
210 and a second measurement unit 212 instead of the signal acquiring
unit 110 and the separation processing unit 112. The first measurement
unit 210 measures the pressure change property based on the cuff pressure
signal output at the specified segment (the segment TB in FIG. 9) where
the constant volume change is given to the cuff 20. The second
measurement unit 212 measures the pulse wave amplitude based on the cuff
pressure signal output at the period of the depressurization control and
at a segment other than the specified segment (namely, a segment where
the constant volume change is not caused (the segment TA in FIG. 9)).

[0114] (With Regard to Operation)

[0115] FIG. 12 is a flowchart illustrating the blood pressure measuring
process according to one or more embodiments of the second example of the
present invention. The processes similar to those in the flowchart in
FIG. 7 are denoted by the same step numbers. Therefore, the description
thereof will not be repeated.

[0116] With reference to FIG. 12, in comparison with the flowchart in FIG.
7, the processes in steps S102 to S114 are inserted between step S8 and
step S15 instead of steps S10 to S14. Further, step S16 is deleted.

[0117] In accordance with one or more embodiments of the present
invention, when the processes in steps S2, S4, S6 and S8 are executed,
the depressurization control unit 104A opens the valve 54 so as to
depressurizes the cuff 20 (step S102). The depressurization control unit
104A determines whether the pressure at the start of the depressurization
is depressurized to predetermined pressure (step S104). The cuff 20 is
depressurized until a pressure difference reaches predetermined pressure
(NO in step S104). When the pressure difference reaches the predetermined
pressure (YES in step S104), the depressurization is stopped (step S106).
That is to say, the valve 54 is closed.

[0118] The second measurement unit 212 acquires the cuff pressure signal
so as to measure the pulse wave (step S108) and calculate the pulse wave
amplitude (step S110). The measurement period of the pulse wave is a
period from the stop of the depressurization to detection of the rising
point of next pulse wave as represented by the segment TA in FIG. 9(B).

[0119] Thereafter, when the maximum point of next pulse wave is detected,
the causing processing unit 106A causes the constant volume change in the
cuff 20 for a constant period (the segment TB in FIG. 9(B)) at specified
timing (for example, predetermined msec time elapses after the maximum
point of the pulse wave) (step S112). The pressure change amplitude with
respect to the constant volume change is measured based on the cuff
pressure signal detected for the period (the segment TB) for which the
volume change is being caused, so that the pressure change property is
calculated (step S114).

[0120] The depressurization control unit 104A determines whether the cuff
pressure reaches the predetermined value as described above (step S15).
Steps S102 to S114 are repeated until the cuff pressure reaches the
predetermined value (NO in step S15). When the determination is made that
the cuff pressure reaches the predetermined value (YES in step S15), the
sequence goes to step S18.

[0121] In such a manner, in accordance with one or more embodiments of the
present invention, because the period for which the constant volume
change is caused is limited to a constant segment (the segment TB), the
separating process in step S16 as described above is not necessary.

[0122] In accordance with one or more embodiments of the present
invention, in steps S18 and S20, the correction processing unit 114 forms
an envelope curve based on the pulse wave amplitude calculated in step
S110, and corrects the formed envelope curve using the pressure change
property calculated in step S114. The correcting method is similar to
that described previously herein.

[0123] In accordance with one or more embodiments of the present
invention, the pulse wave amplitude and the pressure change property (the
pressure change amplitude with respect to the constant volume change) are
calculated during the depressurization control, but they may be
calculated after the end of the depressurization control. That is to say,
when the cuff pressure signal measured during the depressurization
control is used for the calculation of the pulse wave amplitude and the
pressure change property, their calculation timings are not considered.

Third Example

[0124] Embodiments in accordance with a third example of the present
invention will be described below.

[0125] In embodiments of the first and second examples, the constant
volume change is caused successively or intermittently during the
pressure control (the depressurization control) for measuring the pulse
wave amplitude. However, in accordance with one or more embodiments of
the third example, the pressure change property is measured for the
period different from the period of the pressure control for measuring
the pulse wave amplitude.

[0126]FIG. 13 is a diagram illustrating the detection timings of the
pulse wave amplitude and the pressure change property according to one or
more embodiments of the present invention. FIG. 13 illustrates the cuff
pressure as the control value along a temporal axis. In accordance with
one or more embodiments of the present invention, for example, the
pressure change property is acquired for the pressurization period, and
the pulse wave amplitude is acquire for the depressurization period. In
accordance with one or more embodiments the pressurization speed is equal
to the depressurization speed.

[0127] Only portions different from the previous embodiments will be
described below.

[0128] (With Regard to Hardware Configuration)

[0129]FIG. 14 is a block diagram illustrating a hardware configuration of
a sphygmomanometer 1A according to one or more embodiments of the present
invention. The same components as those shown in FIG. 4 are denoted by
the same reference symbols. Therefore, the description thereof is not
repeated.

[0130] With reference to FIG. 14, the cuff 20 in accordance with one or
more embodiments of the present invention includes an air bladder 21A for
blood flow blocking as well as the air bladder 21 for the measurement of
a blood pressure. The air bladder 21A for blood flow blocking is arranged
so as to be located on an upper-stream side of an artery with respect to
the air bladder 21 when the cuff 20 is attached to a measurement site.

[0131] The pressure sensor 32, the oscillation circuit 33, the pump 51,
the valve 52, the pump drive circuit 53 and the valve drive circuit 54
included in the general sphygmomanometer are called as a first
adjustment/detection unit 300. In accordance with one or more embodiments
of the present invention, the main body portion 10 further includes a
second adjustment/detection unit 300A having the same constitution as
that of the first adjustment/detection unit 300. The second
adjustment/detection unit 300A includes a pressure sensor 32A, an
oscillation circuit 33A, a pump 51A, a valve 52A, a pump drive circuit
53A and a valve drive circuit 54A. The pressure sensor 32A, the pump 51A
and the valve 52A are connected to the air bladder 21A for blood flow
blocking via the air tube 31A. Operations of respective section in the
second adjustment/detection unit 300A are similar to the operations of
the respective sections in the first adjustment/detection unit 300.

[0132] In accordance with one or more embodiments of the present
invention, the air bladder 21A for blood flow blocking is provided to the
cuff 20, but not limited to this as long as blood flow is blocked on the
measurement site.

[0133] (With Regard to Functional Constitution)

[0134] FIG. 15 is a functional block diagram illustrating the
sphygmomanometer 1A according to one or more embodiments of the present
invention. FIG. 15 also illustrates the functional constitution of the
depressurization measuring method. Components that executes the similar
processes to those of the functional block shown in FIG. 5 are denoted by
the same reference symbols. Therefore, description thereof will not be
repeated.

[0135] With reference to FIG. 15, in accordance with one or more
embodiments of the present invention, the CPU 100 includes a blood flow
blocking unit 301. Further, the CPU 100 includes a causing processing
unit 106B and a measurement control unit 108B instead of the causing
processing unit 106 and the measurement control unit 108 as described
above. In accordance with one or more embodiments of the present
invention, the pressurization control represents control for changing the
pressure in the cuff 20 to a specified direction (namely, a rising
direction), and the depressurization control represents control for
changing the pressure in the cuff 20 to a direction opposite to the
specified direction (namely, a falling direction).

[0136] The blood flow blocking unit 301 blocks blood flow of the
measurement site using the air bladder 21A for blood flow blocking only
for the period of the pressurization control. The blood flow blocking
unit 301 is connected to the pump drive circuit 53A, the valve drive
circuit 54A and the oscillation circuit 33A. While the pressure in the
air bladder 21A is being detected via the oscillation circuit 33A, the
pump 51A is driven, and when the pressure in the air bladder 21A does not
fluctuate, the drive of the pump 51A is stopped.

[0137] The causing processing unit 106B causes the constant volume change
sequentially during the period of the pressurization control, for
example. The cycle of the volume change in accordance with one or more
embodiments of the present invention may be a predetermined cycle.

[0138] The measurement control unit 108B includes a first measurement unit
310 and a second measurement unit 312. The first measurement unit 310
measures the pressure change property based on the cuff pressure signal
output during the period of the pressurization control. The second
measurement unit 312 measures the pulse wave amplitude based on the cuff
pressure signal output during the period of the depressurization control.

[0139] (With Regard to Operation)

[0140] FIG. 16 is a flowchart illustrating the blood pressure measuring
process according to one or more embodiments of the present invention.
The processes similar to those in the flowchart in FIG. 7 are denoted by
the same step numbers. Therefore, description thereof will not be
repeated.

[0141] With reference to FIG. 16, in comparison with the flowchart in FIG.
7, a process in step S202 is inserted first, and processes in steps S206,
S207 and S208 are inserted between step S2 and step S6 instead of step
S4. Further, a process in step S210 is inserted between step S8 and step
S10. Further, processes in step S218 and step S220 are executed instead
of the processes in step S12 and step S14.

[0142] In accordance with one or more embodiments of the present
invention, before the start of the pressurization, the blood flow
blocking unit 301 expands the air bladder 21A for blood flow blocking so
as to execute a process for blocking a blood flow of the measurement site
on an upper-stream side pressurized by the air bladder 21 (step S 202).
As a result, the pulse wave amplitude is not caused in the air bladder 21
by the intra-arterial pressure change.

[0143] When the blood flow of the measurement site is blocked and the cuff
is pressurized (step S2), the causing processing unit 106B causes the
constant volume change in the air bladder 21 (step S 206). The first
measurement unit 310 acquires the cuff pressure signal (the cuff pressure
data) via the oscillation circuit 33 (step S207) during the period of the
pressurization. The first measurement unit 310 calculates (acquires) the
pressure change property from the acquired cuff pressure signal (step
S208). In accordance with one or more embodiments of the present
invention, because the blood flow on the upper stream side of the air
bladder 21 is blocked at the time of the pressurization, the amplitude of
the acquired cuff pressure signal can be directly measured as the
pressure change property.

[0144] When the pressurization is stopped (step S8), the blood flow
blocking unit 301 exhausts the air from the air bladder 21A for blood
flow blocking so as to end the blood flow blocking (step S 210).

[0145] When the depressurization is started (step S10), similarly to the
normal blood pressure measuring process, the second measurement unit 312
acquires the cuff pressure signal (the cuff pressure data), namely, a
pressure pulse wave via the oscillation circuit 33 (step S 218). The
acquired amplitude of the pressure pulse wave (the pulse wave amplitude)
is calculated (step S220). In accordance with one or more embodiments of
the present invention, because the constant volume change is not caused
at the time of the depressurization, the acquired cuff pressure signal
represents the pressure pulse wave.

[0146] In accordance with one or more embodiments of the present
invention, the correction processing unit 114 forms the envelope curve in
steps S18 and S20 based on the pulse wave amplitude calculated in step
S220, and corrects the formed envelope curve using the pressure change
property calculated in step S208. The correcting method itself is similar
to that as described above.

[0147] In accordance with one or more embodiments of the present
invention, the pressure change property (the pressure change amplitude
with respect to the constant volume change) and the pulse wave amplitude
are calculated during the pressurization control and the depressurization
control, respectively. However, their calculating timings are not
considered as long as the cuff pressure signals detected during the
respective controls are used for the calculation of the pressure change
property and the pulse wave amplitude.

[0148] While the invention has been described with respect to a limited
number of embodiments, those skilled in the art, having the benefit of
this disclosure, will appreciate that other embodiments can be devised
which do not depart from the scope of the invention as disclosed herein.
Accordingly, the scope of the invention should be limited only by the
attached claims.